Reforming catalyst and method for preparing the same



NOV. l0, 1953 L, Q DRAKE ET AL 2,658,931

REFORMING CATALYST AND METHOD FOR PREPARING THE SAME Filed June 12, 1952 'Broadly, the instant :invention comprisesV the Patented Nov. 10, 1953 REFORMING CATALYST YANDllIETHOD FOR f APREPARING THE SAME Leonard'CDrake, Wenonah, and Robert L. Smith, Y Pitman, N.J., assignors to Socony-Vacuum Oil Company,.lncorporated, a corporation of New York Alwiicanon .rune 12, 195e, serial No. 293,132

, '1" This invention relates to ian improved reforming catalyst andv to f ajmethod for, preparing f the same. More particularly, the present invention isdirected to a processfor reforming petroleum hydrocarbons in the ,presence of a catalyst containing chromium,.carbon, nitrogen, andk oxygen combined in the form which results upon thermal decomposition and waterextraction of' an alkali metal chromicyanide. Y t

' Reforming operations wherein saturated gasoline fractions comprising straight run gasolines, natural 'gasolines rete.V `are treated j to improve the antieknock characteristics thereoffare well known inthe petroljejnnindustry. Straight run gasolines generally 'contain naphthenic hydrocarbons, particularly j *cyclohexane compounds, and parai'dnic hydrocarbons which are'usually of straight chain orfjSlehtlv branched ,chain vstru@- ture, as well Vas varying proportionsofvaromatic hydrocarbons. ,During reforming, a multitude'of reactions take place',` vincluding isomerization, ldehydrogenatiom cyclization,v etc., to yield a product of increased aromatic content." Ihus,'in reforming, itis desired to dehydrogenate the naphthenic hydrocarbons to produce'aromatics and'to cyclicize the straight chain parafnic hydrocarbons `to form aromatics, thereby increasing the octane number of the resulting stock. Y

Many xdifferent catalystshave been proposed for Areactions of the above type. Thus, alumina,

Anatural clay, kieselguhr, silica gel, silica-alumina gel, or `other supportsY with relatively, porous structures and Y appreciable vsurfaces -have been impregnatedlf Withlliarious `oxidesffof. metals' of lgroups V, VI and VII or transition group" elements. Co-precipitated orA ccgelledjcomposites containing one ormore of the above Ymetal oxides have also'been venri'ployed as reforming'catalysts. Probably, the most'widely studied catalysts have comprised various intimate mixtures of chromia and'alumina, suchiasactivated bauxiteimpregf 11l claims. (cinco-66s) nated vwith Crzoggcoprecipitatedcomposites of 4chromia and alumina; and''so-gelled'.chromiaaluminagc'omposites.;as' 'j l 'l In accordance `with the rpresent invention, an

'improved catalyst has been discovered Yhaving a 'somewhat ygreater reforming activity! than cogelled vchromia-alumina composites i heretofore proposed forzcommeicialv `-reforming operations.

provision of-va; reforming catalyst consistngessentially of chromium, carbon, nitrogen, and oxygen ,combined inthe formgwhich resultsupon thermal decomposition and subsequent water ex- ,.tration gf an alkali; mtal-Clirmiyaaidaffhe f csfgqnibined suon as to. form ania1i a11-meta1 invention further comprises a method for producing the catalystfand the use thereof in catalyzing the reforming of light petroleum fractions, particularly those hydrocarbon fractionsy containing a'substantial proportion of compounds having chains of' six 'or more 'carbon' atoms 'to increase the aromatic content thereof. "'The present method of catalyst preparation ,inv` volves'thermaldecomposition of an alkali Ametal chromicyanidein the absence of oxygen' and's'ub# sequent extraction or leaching of the Vproductfnf decomposition 'With water.- The resultant material has been found to have a high surface far'a andY to be an active catalyst inthe reforming'of light hydrocarbons The material is of a Vcoinplex nature vand 'contains chromium, nitrogen, carbon, 4and oxygen, `The exact structuralconguration in which'theseleleinents are combined is not knovvn'with' certainty.y X-ray examination of the materialha's shown the presence of gamma-CrN. The manner of introduction" of oxygen into the materialk is not fully understood. It appears, however, that it is introduced during contact of the-decomposed product with r Water, While water-soluble compounds are being *Instead of preparing andf-j isolating aan@ alkali metal chromicyanide, it has further been f ound that mixtures of a `chromicjsalt and alkali metal Cyanide may be heated-'together to decomposi:

tiontemperature and thevdecomposed product thereafter .extractedwith water. V It would ape A`pear that the Malkali vmetal:-chromicyanideiis formed in situ-by such process.-V LThe particular lchromiasalt usedV inisuch'y method rof preparation is onehaving ananionwhich upon ,cor'nbinationV Withfanz` alkali metal Will form a watersoluble salt., fIhus, the chromic salts of mineral; acids may suitably be employed, such as chromic chlo- `ride,chrornic sulfate, and chromic nitrate. Y Other salts of chromiuml falling Within 'the above categoryvmayv also.A be used.y i TheV particular choice of l,chro'mic-salt Willdepend largely upon economic factors, landv'generallya readily available, relatively inexpensive salt will be used, Y'he proportion ofiichrlomic salt and lalkali.,metal..cyanide 3 chromicyanide. Generally the mole ratio of chromic salt to alkali metal cyanide will be in the range of 1 to 6. The mixture is preferably but not necessarily prepared as an aqueous slurry.

The alkali .metal claromicyanide` ormixture of chromio'salt and alkali metal cyanide is heated to decomposition temperature in the absence of oxygen and held at such temperature for a period of time sumeient to insure;.decomposition. Ame temperature of decomposition will, of course, de, pend upon the particular alkali metal chromicyanide or mixture of chromic-.saltand f illil4 met cyanide employed but is generally'in thealfge of about 800 F. to about 14oo F. As ag'er'ral rule, temperatures in excess of about 1400" E'. are to be avoided since they leadi'to.productsof-de creased surface area. The time duririgxwh such temperature is maintained is ordinarilyleor caibnl'monoxidmor thepr'esence'of .nitroeen. 'Or under 'reduced/pressures 'approaching vacuum. i. at a pressure'of 4 about Qne'milimeter of mercury or less.v Itv is important'for success or the instant method of catalyst preparation` that nooxygen gasbe present. `The `ma-l terial` resulting Vfrom the aboveflglesfrlbed 1decomposition is' characterized by -a Vrelai-, iyely high sui'ace; area; and high c atalytioactivity: lin the reforming ofetroleum hydrocarbons.

at a space rate of 3 volumes of n-heptane per hour per volume of catalyst and a temperature of 900 F. and a pressure of one atmosphere. The catalyst was subjected to preliminary treatment 5 at 900D forgjuhour with'hydrogen before the ruri.- A conversion to toluene of 46 yiritile per cent resulted.

Example 2 143@QA'mixturebf'Sllfgrams KCN and 615 grams of OrCl3-6H2O was mixed with water to form a slurry atroomtemperature. Some gas was @Illlld and the mixture became gray. The slurry Y :Wasi-.driedwitlt-hydrogen passing through (air 1D excluded) and thetemperature gradually raised to l 1949" Ryyithnhydrogen passing through for 21/2V hrs,"'during which time water was removed. Aitergoqgling to room temperature in the presence of hydrogen, the product was Water-Washed 20 tofgremore.KQNandthen pelleted. The pellets were their dredty passing hydrogen 'over'V them for onehour iat 4192.5a The surface are@ lf these pellets 'Was l`87 "sq. meters per gram. Xf-rayarialy'sis Shwdtheprdducf 6 0 @9h .in 25 gammaQCrN. The 'product upon chem cal analysis, #deemed accurate Within experimental error to 42:2pe11. cent. "was 'found t9] contain@ per cent Cr, v6 per cent C; 27 per cent Q; 5 per centN, .5 per cent BL and'vl per' cent'i/.Qlatile 30 mat6'1`.'9.1

. The. material lyrasfexceptionally.: .Catal active ffOr thedehydrocyclizatin having aninifil that shown by" @viper cent1 mgszaaly'st f out' by, alprel The follQwirfie exampleswilil serve @illustrate the invention 'Without limiting the same Example" 1 'Ai sampleof crystalline KaCr (CN) s -l-was 'prew24-gramsinv 300cc. of 1II2O)yand KEN-*(150 grams iff-.600 ec. rif-H2O) and agitatmg the mixtu-re for-1/2Jhour.d-The resultant'mat'eiial was 'filtered and vthenitrateWas boiled until `-it was about% of' its original volume. `'Ill-ureavolumes ofwan alcohol-mixture consistingfof `130--'oli1frji e oen-t ethanolvandilyolumelper cent methanol were added'tolower the soli-ibility. Themi-xturerwascoolede-andthe crude product ltered.

The tan-colored resid-ue wasdissolved in'a-'minii mum'- of--wat'er,ltered, and 34 volumes" ofthe above --ind-icated alcohol Y mixture was -added to thefltrate.-fTh-is mixture was 'cooledv and-the precipitate-present was removed by'ltration. The-residue was evacuated to remove residual solvent-after which 'I4 g-ramsfof potassium chromieyanide remained, correspondingto a 59% tion catalystVv employing a charg of ln-"heptane .60 )These 'results'.anefpresented graphically -ure .l V.of theaattachedfdrawing... Atri-hetend `tof :3:1/2' hours,Y itewillihenotedthat the mole' 'percent -conversionzhadideclined m37. A'hydrogen treat, at this point, under the reaction Acouditioris-.served Jdreigen :was introduceo'lover .a period. .of abouti() minutes. and-fthe amountpof hydrogen-so intro.- Aduced .-itasxahout 3e mo1e..i1er;.no1e.,of initial .n.-heptane charge. V.uzillfloe apparenti-treat.,-

70 fment ofiithei reaction `.mixture withihydrgenaat gen catalyst was'also tested for naphthene conversion to aromatics. The test conditions were:

Charge Methylcyclohexane. Temperature 932 F. L. H. S.V 1.l Pressure (hydrogen) 100 p. s.i. g. Hydrogen to hydrocarbon ratio 5. Time 2hrs.

The results of such test, together with results for a commercial chromia-alumina catalyst (30 per cent CrzOa-7O per cent A1203) tested under identical conditions are tabulated below:

. Liquid Gas, Catal st Wt y Vol. Vol. Percent Percent Percent Charge Olens Aromatics Cr-C-N-O Catalyst (Example 1.3 77. 7 7. 8 Chromia-Alumina Catalyst 0. 6 47. 4 9. 7

Charge Methylcyclohexane.

Temperature 900 F L. H. S. V .1.

The results of such test, together with results for a commercial chromia-alumina catalyst (30 per cent Crza-70 per cent A1203) tested under identical conditions are presented graphically in Figure 2 of the attached drawing. In this case also, a hydrogen treat after the conversion had declined to a point below the initial conversion was observed to increase the activity of the catalyst, thereby affording a higher overall conversion of the methylcyclohexane charge to toluene. As will be noted, the activity of the instant catalyst was appreciably greater than chromiaalumina catalyst employed under identical reaction conditions.

`Eztample 3 A catalyst was prepared following the procedure of Example 2 except that 678 grams of NaCN were used rather than KCN. 'I'he resulting pelleted product had a surface area of 206 square meters per gram. Chemical analysis, deemed accurate within L2%, showed the product to contain 69 per cent Cr, 3 per cent C', 19 per cent 0, 2 per cent N, and 2 per cent Na and 7 per cent volatile material.

This catalyst was tested for conversion of naphthenes to aromatics by passing methylcyclohexane over the catalyst at a liquid hourly space velocity of one, a temperature of 932 F., a hydrogen pressure of 100 p. s. i. g. for 2 hours using a hydrogen to hydrocarbon ratio of 5 to 1. The conversion of methylcyclohexane charge to toluene under such conditions was 41 per cent.

Eample 4 A mixture of CrCla-GHzO (10.2 grams) and KON (15 grams) was ground together and heated without the addition of water in the presence of "6 hydrogen for 1:5 hours at 1000 F.' The product of decomposition was extracted with water until v free of soluble matter.

The resulting material, after drying, weighed v2.7 grams. X-ray analysis lof thismaterialshowed the presence o f crystalline gamma-CIN.

Example 5 Arcatalyst was prepared by the method of Example 1 employing KaCr(CN)e except that it was decomposed while evacuated to a pressure of about 0.01 millimeter of mercury rather than in a hydrogen atmosphere. The resulting materialafter water extraction to free the same of soluble matter was found to have a surface yarea of 264 sq. meters/gram, indicative of high Vcatalytic activity.

Example 6 A catalyst wasv prepared by the method of Example 1 employing KaCr(CN)s except that it was decomposed in an atmosphere of nitrogen rather than in hydrogen. The resulting material after water extraction was found to have a surface area of 151 sq. meters/gram, indicative of high catalytic activity. i Y

Y Example 7 l A catalyst Vwas prepared by the method `of Example 2 employing anV aqueous slurry of CrCl3 61-120 andKCN except thaty nitrogen rather than hydrogen was used as purge gas during the thermal decomposition. The resulting material, after water extraction to free the sa'me of soluble matter, was found t'ohavea surface area of 221 sql meters/gram;

This catalyst was tested for dehydrocyclization activity. The test conditions were.:

Charge n-Heptane. Temperature 900 F. L. H. S. V 1. Pressure 1 atmosphere.

The mole per cent conversion to toluene was determined after the first half-hour and there-l after at one-hour intervals. The results were as follows:

Mole Percent Tolene Time (Hours) These results are presented graphically in Figure 3 of the attached drawing in which results obtained under identical test conditions using a. commercial chromia-alumina catalyst (30 per .cent Cr203-70 per cent A1203) are also shown.

2. A method of producing a reforming catalyst -ccmprisingmixing an alimentan'cyanidefwith i chromic vsalti the anion -of which forms av substantially .completely water-soluble alkali metal compound, the proportion of .said alkali metal Ycyanide and said chromic salt being such-as to form an alkali metal hromicyanide,heating the resulting mixture to decomposition temperature in the Substantial absente .O f @weer @aconteciins the eredutef deqempeeitenwith-wateruntil ,lfee of semble metten it Af method Of. producing; e reforming @attest eeemrisieemirins mais@ metal cyanide with a hreni mineral. eelt. the vroem-tien 1f-.Seid

A,alkali metalcyanideand said 'chrorncsalt being mosphere and leaching the productl of decompos'itionV with Water until free o'ffsolulolevmatter.

5. A method of producing a reforming catalyst comprising mixing potassium cyanide with chroiirilisznleride. heating 'the resulting. mixture t0 iflecempositien temperature thesubstaetiel ebsgnfie of. Oxygen en@ tempting the prduCt-Qf 8 bined in the form which results upon thermal decomposition of an alkali metal chromicyanide in an gxygenf-free atmosphere and extraction of the product of decomposition with Water until free of soluble matter.

'7. A method of producing a reformngcatalyst comprising effecting thermal decomposition of sodium chromicyanide in an oxygen-free atmos phere and leaching the product of decomposition with Water until free'of soluble matter.

8. A method of producing a reforming catalyst comprisnglmixing sodium cyanide with chromio chloride, heatingthe resulting mixture to decom.- position temperature `in the substantial absence of oxygen and contacting the product of decomposition with .water until free of soluble matter.

'9. A processV for increasing the content of aromatics ina hydrocarbon mixture, said process comprising contacting said hydrocarbon mixture `with the catalyst of claim 6 under reforming con-i ditions.

10. A process for converting nflieptane to toluene, which comprises contacting a charge of n-heptane with the catalyst of claim 6 under dehydrocyclization conditions.

11'. A process for converting methylcyclohexane to toluene, which comprises contacting a charge ofmethylcyclohexane with the catalyst oi claim 6 under reforming conditions.

LEONARD C. DRAKE. ROBERT L. SMITH.

No references cited.

env... W 

6. A REFORMING CATALYST CONSISTING ESSENTIALLY OF A MAJOR PROPORTION OF CHROMIUM AND MINOR PROPORTIONS OF CARBON, NITROGEN AND OXYGEN COMBINED IN THE FORMED WHICH RESULTS UPON THERMAL DECOMPOSITION OF AN ALKALI METAL CHROMICYANIDE IN AN OXYGEN-FREE ATMOSPHERE AND EXTRACTION OF THE PRODUCT OF DECOMPOSITION WITH WATER UNTIL FREE OF SOLUBLE MATTER.
 9. A PROCESS FOR INCREASING THE CONTENT OF AROMATICS IN A HYDROCARBON MIXTURE, SAID PROCESS COMPRISING CONTACTING SAID HYDROCARBON MIXTURE WITH THE CATALYST OF CLAIM 6 UNDER REFORMING CONDITIONS. 